A wind turbine transfers the energy of moving air into electrical energy. The moving air accelerates the rotor of the wind turbine. The rotation of the rotor is transferred to an electrical generator. The electrical generator transforms the rotational energy into electrical energy.
In the last years the concept of a direct driven wind turbine was established. In a direct driven wind turbine the rotational energy of the rotor is transferred to the generator directly without the use of a gearbox.
In a direct driven wind turbine the rotor of the wind turbine is directly connected to the rotor of the electrical generator. The chain of mechanically connected parts leading from the rotor of the wind turbine to the rotor of the generator is called the drive train of the wind turbine.
To allow the rotational movement and to provide the necessary stability of the rotating parts, the drive train is mounted with at least one bearing. This bearing allows the drive train to rotate. At the same time it provides the necessary stability by supporting the radial and axial loads and the bending moments present in the drive train.
WO 2011/003482 A2 describes a wind turbine main bearing realized to bear a shaft of a wind turbine. The bearing comprises a fluid bearing with a plurality of bearing pads.
To perform a service at this bearing and to exchange the bearing pads, the bearing has to be taken apart. The upper part of the outer bearing shell and the side walls of outer bearing shell are removed to gain access to the bearing pads. For the exchange of the bearing pads the shaft of the wind turbine needs to be lifted by help of a lifting arrangement. For this service a lot of space needs to be provided in the nacelle of the wind turbine. In addition the dismantling and assembling of the bearing needs a long time. Thus the service of the main bearing is very expensive and time extensive.
It is also known to dismantle the rotor of the wind turbine by the use of a crane to get access to the main bearing. Then the main bearing is disconnected from the wind turbine and is lowered to the ground to perform the necessary service and exchange the sliding pads. The bearing is then again connected to the wind turbine and the rotor is attached to the main bearing.
It is also known to perform service within the wind turbine. The rotor of the wind turbine is fixed to the nacelle to achieve a load-free bearing. The bearing shells are then separated to gain access to the sliding pads to examine and exchange them. After the service the bearing needs to be assembled again. The bearing shells need to be adjusted. This method also needs a big space within the nacelle or the hub of the wind turbine to handle the shell of the bearing. There is also the problem of dust and foreign particles that can enter the open bearing during the time of service and stay undetected in the bearing when the service is finished and the bearing is closed again.